Trench ld structure

Abstract

A lateral conduction MOSFET has a trench between and separating surface source and drain electrodes. A gate insulation lines one vertical wall of the trench and a polysilicon gate mass is disposed adjacent the gate insulator and fills a portion of the width of the trench. The conduction path from surface source to surface drain is thus elongated by the periphery of the depth of the trench without using excessive surface area for the MOSFET die.

1 . A lateral conduction MOSFET comprising a semiconductor die having a body of one of the conductivity types and having first impurity concentration and having an upper surface layer of said one of the concentration types and having a higher concentration than said first concentration; a plurality of parallel spaced trenches formed in said die and extending from the top of said upper surface and through said upper layer and into said body of said die and separating said upper surface layer into a source region on one side of said trench and a drain region on the other side of said trench; a thin gate oxide lining at least one side wall of said trench and a conductive gate electrode having a given width filling a portion of said trench and in contact with the surface of said thin gate oxide and being spaced from the opposite wall of said trench by a large multiple of the thickness of said gate oxide; and source and drain electrodes connected to said source region and drain region respectively.  
   
   
       2 . The device of  claim 1 , wherein said semiconductor die is monocrystalline silicon.  
   
   
       3 . The device of  claim 1 , wherein said body and said upper surface layer have the N conductivity type.  
   
   
       4 . The device of  claim 1 , wherein said conductive gate electrode is polysilicon.  
   
   
       5 . The device of  claim 1 , wherein said conductive gate is rectangular in cross-section.  
   
   
       6 . The device of  claim 1 , wherein the space between said gate electrode and said opposite wall is filled with an insulation material.  
   
   
       7 . The device of  claim 6 , wherein said insulation material is an oxide.  
   
   
       8 . The device of  claim 7 , wherein said semiconductor die is monocrystalline silicon.  
   
   
       9 . The device of  claim 7 , wherein said conductive gate electrode is polysilicon.  
   
   
       10 . The device of  claim 9 , wherein said conductive gate is rectangular in cross-section.